To develop effective preventative and therapeutic regimens for cardiovascular disease, it is important to understand control of the functional state of the vascular endothelium. Changes in blood flow and pressure alter the functional state of the endothelial cells (EC), which are naturally subjected to physical forces in situ. Thus definition of the precise roles of physical forces in maintaining normal and in producing pathological EC behavior is important. Shear stress, the force tangential to the EC resulting from blood flow is considered to be the mechanical force that is most injurious to the endothelium. Whether pulsatile variations in shear stress differ as a stimulus from steady shear stress is unknown. This research will analyze the mechanisms of adaptive EC responses to steady shear stress, and compare these with responses to pulsatile shear stress. How hemodynamic information is transduced across the cell membrane and how this information is then conveyed to other parts of the cell will be investigated. How the cell responds in terms of changes in protein synthesis will be investigated. Specific Aims follow a sequence of stimulus and response, testing the following hypotheses: 1. that transduction of shear stress information consists of alterations in ion channels leading to membrane hyperpolarization, 2. that an increase in cytosolic calcium acts as a second messenger for transduction of shear stress signals, and 3. that shear stress changes synthetic rates of specific proteins. The proteins will be identified and the kinetics of change in these proteins produced by shear stress will be investigated. The long term goal is to understand the adaptive response of EC proteins to shear stress, and to investigate how transduction events alter synthesis of these proteins. These studies will involve continuous measurement of membrane potential and cytosolic calcium using spectrofluorometric dyes and isotopic efflux. Radiolabelled proteins will be studied by 2-D gel electrophoresis, fluorography, digital analysis of gels, fractionation, antibody reactivity, and peptide sequencing. EC abnormalities may contribute to atherosclerosis, thrombosis, hemostatic disorders, as well as to inflammation, immune reactivity and tumorigenesis. How shear stress alters EC function mill elucidate these disease processes.